Today's Veterinary Practice

SEP-OCT 2018

Today's Veterinary Practice provides comprehensive information to keep every small animal practitioner up to date on companion animal medicine and surgery as well as practice building and management.

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PEER REVIEWED 60 SEPTEMBER/OCTOBER 2018 Each segment of the gastrointestinal tract (stomach, duodenum, jejunum, ileum, and colon) can be ultrasonographically distinguished based on wall layering and thickness. Ultrasonographic measurements of the individual wall layer thicknesses of the canine duodenum, jejunum, and colon have been proposed to assess gastrointestinal diseases that target specific wall layers or the entire intestinal wall segment. 24 TABLE 3 lists differences in overall wall thicknesses of the different intestinal segments as well as the appearance of the wall layering in dogs and cats .1,25-30 Dog The canine gastric submucosal layer is thin like that of the small intestine ( FIGURE 13A AND 13C ). Complete evaluation of the stomach can be limited by the presence of food material and/or gas, which is a common feature of the canine gastrointestinal tract. The transition between the pyloroduodenal angle and proximal duodenum can be identified; the pyloroduodenal junction and cranial duodenal flexure are in a more lateral position in dogs than in cats. An intercostal right-sided approach may be necessary to identify the cranial duodenal flexure in a dog. The canine duodenum is the thickest portion of the small intestine in the dog and normally has a thicker mucosal layer than the jejunum. The duodenal thickness in normal dogs varies according to weight. 31 The major duodenal papilla is located near the cranial duodenal flexure and appears as a hyperechoic, spindle-shaped structure located in the submucosa, with an area of eccentric thickening where the papilla is located ( FIGURE 4 ). In the jejunum, the mucosal layer is the thickest layer, whereas the submucosa and the muscularis are thinner. In the ileum, the wall layers of the muscularis, submucosa, and mucosa are more equal in width than in the duodenum and jejunum. The large canine cecum is usually gas-filled, making it difficult to identify as a separate structure from the ascending colon. The colon is the thinnest gastrointestinal segment. It can be traced from the pelvic inlet to the ileum in both dogs and cats, and its anatomic positioning is similar in both species. Cat In cats, the rugal folds of the fundic portion of the stomach have a hyperechoic, prominent submucosal layer ( FIGURE 14A ) secondary to fat deposition. As in dogs, evaluation of the stomach can be limited by the presence of food material and/or gas; however, gas is less common in the feline gastrointestinal tract. The rugal folds in the region of the fundus become smaller at the transition to the gastric body and pyloric antrum ( FIGURE 13B ). As in dogs, the transition between the pyloroduodenal angle and proximal duodenum can be identified; however, the pyloroduodenal angle is narrower and in a more midline and dorsal position in cats than in dogs. The mucosal layer of the feline duodenum is thinner when compared with the duodenum in the dog. This is similar to that of the feline jejunum. The location and appearance of the major duodenal papilla are similar to those in the dog. TABLE 3 Normal Wall Thicknesses of the Gastrointestinal Tract of Dogs and Cats DOG CAT Stomach 3–5 mm 25 2 mm (inter-rugal) 26,27 and 4 mm (rugal fold thickness) 26 Duodenum <5 mm 28 2.0–2.5 mm 27 Jejunum 2–5 mm 29 2.5–3.2 mm 27 ; thickest segment in the cat Ileum 2–4 mm 1 Colon 2–3 mm 29 1.4–2.5 mm 27,30 Superscript numbers are reference citations.

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